My career goal is to improve health outcomes for aging HIV-infected and at risk communities and to support the development of health promoting interventions tailored to socially marginalized, resource-constrained, and clinically vulnerable members of these communities. Frailty is an important age-related state of increased vulnerability to stressors that results in early death and a wide range of adverse age-associated clinical outcomes including increased hospitalization, disability, and institutionalization. Consequently, frailty has been identified by the Institute of Medicine as a top target priority are for health care improvement in the U.S. Early data have suggested an increased occurrence of frailty among aging HIV-infected persons. The epidemiologic and biological factors that determine transitions between frailty states (frailty progression and recovery) are not well-characterized. The proposed studies are nested in the AIDS Linked to the IntraVenous Experience (ALIVE) cohort, representing aging, minority injection drug users (IDUs) at the greatest risk for frailty-related consequences. Aim 1 utilizes longitudinal ALIVE data to examine the role of HIV and multimorbidity on frailty progression and recovery among aging HIV-infected and epidemiologically comparable HIV-uninfected IDUs. Aim 2 will longitudinally assess the relationship of inflammation-related biological markers with frailty transitions. Aim 3 will determine the feasibilty and define optimal trial elements for a mobile health (mHealth) enhanced exercise intervention to improve frailty parameters among aging HIV-infected persons. The proposed career development plan will expand my technical skills through additional expertise in the following domains: (1) transition modeling and analysis of complex longitudinal data; (2) application of mHealth technologies to health behavior promotion; (3) design and implementation of physical activity interventions for resource-constrained, frail, aging HIV-infected persons. I will be well supported within the Department of Medicine at Johns Hopkins University and will benefit from the excellent research infrastructure of the ALIVE study and other centers and institutes at Johns Hopkins University. With increasing survival but increased risk of multimorbid disease among aging HIV-infected populations, research on the epidemiologic and biological aspects of aging with HIV have become an NIH priority. Frailty represents an important age-related syndrome of significant